Assessment Comments
Assessment remains based on (1) observations and photo documentation by IDNR staff in 2005, (2) results of weekly chemical monitoring conducted by IDNR staff from May 2005 through July 2006, (3) IDNR/UHL biological monitoring in 2006, 2009 and 2010, and (4) bacteria monitoring in 2009 conducted as part of IDNR Snapshot monitoring.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters. Thus, for the current (2012) assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]
SUMMARY: The general uses of this stream remain assessed (monitored) as "not supported" due to a history of impacts of poorly-treated wastewater discharged to the stream. In addition, the presumptive Class A1 (primary contact recreation) uses remain assessed as "not supported" based on violations of Iowa's narrative water quality criteria due to discharge of poorly-treated wastewater to this stream segment. Also, monitoring conducted from 2006-09 as part of IDNR Snapshot water quality monitoring has shown that levels of indicator bacteria (E. coli) far exceed Iowa’s criteria to protect the presumptive Class A1 (primary contact recreation) uses of this stream: this is a new impairment for this stream segment. The presumptive Class B(WW1) aquatic life uses of this stream remain assessed (monitored) as "not supported" due to (1) impacts of poorly-treated wastewater discharged to the headwaters of this stream and (2) results of IDNR/UHL biological monitoring in 2006, 2009 and 2010.
The sources of data for this assessment include (1) results of observations and photo documentation by IDNR staff in 2005 and (2) results of weekly chemical monitoring conducted by IDNR staff from May 2005 through July 2006 at three locations from North Liberty downstream to First Avenue in Coralville, IA, (3) IDNR/UHL biological monitoring at three locations in the segment in 2006 and one location in 2009 and 2010 and (4) bacterial monitoring conducted from 2006 through 2009 at five stations monitored as part of the IDNR Snapshot volunteer water quality monitoring program. This stream was not assessed for purposes of Section 305(b) assessment or Section 303(d) listing prior to the 2006 assessment/listing cycle.
EXPLANATION: A survey conducted in October 2005 by IDNR staff documented accumulations of sewage sludge in Muddy Creek downstream from the North Liberty wastewater treatment facility. Accumulations of sludge were up to 12 inches deep and occurred up to one-half mile downstream from the wastewater treatment facility. In addition, results of water quality monitoring from May 2005 through July 2006 show acutely toxic levels of ammonia occurring on December 5, 2005. The accumulations of sewage sludge and poor water quality conditions observed and reported by IDNR staff potentially violate several of Iowa's narrative water quality standards (IAC 61.3(2)) designed to protect general uses of Iowa's surface waters (e.g., livestock and wildlife watering, aquatic life and non-contact recreation):
--such waters shall be free from substances from point source dischargers that will settle to form sludge deposits;
--such waters shall be free from floating debris, oil, grease, scum and other materials from wastewater discharges or agricultural practices in amounts sufficient to create a nuisance;
--such waters shall be free from materials from wastewater discharges or agricultural practices producing objectionable color, odor, or other aesthetically objectionable conditions;
--such waters shall be free from substance attributable to wastewater discharges or agricultural practices in concentrations or combinations which are acutely toxic to human, animal, or plant life.
Based on the information received by IDNR on this stream, the general uses were assessed (monitored) as "not supported" due to water quality impacts from poorly-treated domestic sewage being discharged to Muddy Creek. Waters assessed as “monitored/not supported” are considered appropriate for addition to Iowa’s Section 303(d) list of impaired waters.
The presumptive Class A1 (primary contact recreation) uses of Muddy Creek are assessed (monitored) as "not supported" due to violations of Iowa’s water quality criteria for indicator bacteria. The geometric means of indicator bacteria (E. coli) in the 10 samples collected during the recreational seasons of 2006, 2007, 2008 and 2009, respectively, at each of the five IDNR Snapshot monitoring station in this assessment segment were as follows:
1. Muddy Creek at Golf View Dr. (MCB), STORET station 952116: 200-09 geometric means were 1,244, 1,529, 1,100, and 323 orgs/100 ml;
2. Muddy Creek at 1st Avenue (MC3); STORET station 952077: 2006-09 geometric means were 846, 402, 1,220, and 580 orgs/100 ml;
3. Muddy Creek at Kate Wickham Elem. (MC2); STORET station 952076: 2006-09 geometric means were 719, 441, 1,340, and 514 orgs/100 ml.;
4. Muddy Creek at Front Street (MC1); STORET station 952075: 290, 516, 592, and 293 orgs/100 ml;
5. Muddy Creek at West Cherry St. (MCA); STORET station 952115: 263, 274, 371, and 250 orgs/100 ml.
From 56 to 90% of the samples at each of the Snapshot sites exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported".
The assessment of the presumptive Class B(WW1) aquatic life uses was based on data collected in 2006, 2009 and 2010 as part of a IDNR/UHL stream biological monitoring project. A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2006 FIBI scores were 2, 24 (fair) and 42 (fair). The 2006 BMIBI scores were 35, 52 (fair). The 2009 FIBI score was 13 (poor) and the BMIBI score was 54 (fair). The 2010 FIBI score was 30 (fair) and the BMIBI score was unavailable. The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI BIC 1/5 times and passed the BMIBI BIC 2/3 times in the last five years. Even though this segment failed the FIBI BIC and passed the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small general use stream and doesn’t fall in the calibrated watershed size.
Prior to the changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this stream was classified only for general uses due to the inability of the stream to support a viable aquatic community at low-flow conditions. IDNR’s existing biological assessment protocol, however, was calibrated to aquatic life reference conditions in larger wadeable streams with perennial flow. The aquatic environment of most headwater streams is one of extremes in water quality. Consequently, intermittent headwater streams tend to have biological diversity that is low relative to more stable aquatic environments of larger streams with perennial flow. Thus, the use of biological assessment methods developed for the ecologically more stable and diverse streams will likely overstate the existence of impairment in headwater streams.
CONCLUSIONS: Based on the documentation of the impacts of poorly-treated wastewater in Muddy Creek, the general uses of this stream, as well as the presumptive Class B(WW1) aquatic life uses and the presumptive Class A1 primary contact recreation uses of this segment, remain assessed as impaired. The presumptive Class A1 (primary contact recreation) uses are now also impaired due to violations of Class A1 water quality criteria for indicator bacteria (E. coli). Recent (2011) observations by volunteer monitors suggest improved water quality in Muddy Creek (D. Ratliff, personal communication). Upgrades to the wastewater treatment facility at North Liberty have eliminated the accumulations of sludge in pools of Muddy Creek. Based on these observations, additional monitoring is needed to determine whether the impairments of general uses, aquatic life uses, and primary contact recreation uses can be removed. Despite potential improvements in the water quality conditions of this stream, this impairment remains on Iowa's impaired waters list.
